Tomorrow, members of my family and parish community and I will again take part in the annual March for Life in Washington, D.C. Why do we go to all the trouble and expense to hire buses, book hotel rooms, bundle up and brave the freezing weather to march yet again in our nation’s capital?

Because we’re not only against abortion — we’re pro-life. There are many different forms of argument in the battle against abortion. There is the sentimental argument: “It is heartbreaking to think of all these dear, tiny babies being slaughtered in their mother’s wombs!” There is the utilitarian argument: “We’re committing societal suicide. Our birth rate is falling, and there will not be enough young people to support us in our old age.” Then there is the human-rights argument: “The first and most basic human right is the right to life.” The moral argument states: “Do not kill. Taking a human life is wrong.” The economic argument is: “Children are consumers and future workers. When we kill off a generation of children, we are destroying economic growth and future prosperity.”

All of these arguments are valuable in the overall debate, but we must never forget the fundamental pro-life argument: the theological one. Every argument is a theological argument, and so it is in the great abortion conflict. The theological argument is simple: “We are in favor of human life because every individual human being is a unique image of God himself. We are, therefore, against abortion because it destroys a human life.”

From the beginning, Catholic theology, rooted in the ancient Hebrew worldview, understood that men and women were created in God’s image and, therefore, each human being is an eternal image of God the Creator and Father of all. Writing in the third century, St. Hippolytus says, “The saying, ‘Know yourself’ means, therefore, that we should recognize in ourselves the God who made us in his own image, for if we do this, we in turn will be recognized and acknowledged by our Maker.”

We are created in God’s image, and that image is indelible. It may be distorted, but it cannot be destroyed. As St. Augustine teaches, God’s image in us is wounded by original sin. At the heart of the Christian faith is the transaction between God and his creatures, in which, by the reconciling death of Christ, the wound of original sin is healed and man can begin the long journey to his restoration and eventual perfection. In the words of Jesus, we are to “be perfect as God is perfect” (Matthew 5:48). This miracle of grace is called theosis (divinization). As St. Hippolytus writes, “In the beginning God made man in his image, and so gave proof of his love for us. If we obey his holy commands and learn to imitate his goodness, we shall be like him ... for he has given us a share in his divinity.”

And so, Catholic theology affirms the essential dignity of each human being, but it also affirms the eternal destiny of each human being: We are made in God’s image, and our final destiny is to be restored perfectly to God’s image — each soul a shining star uniquely fashioned and finally destined to reflect God’s glory.

There are three theological attacks on this fundamental Christian doctrine. The first comes from the atheists, who deny the existence of God, and, therefore, must deny the essential dignity and destiny of the human person. If there is no God, then human beings must be the simple result of blind evolutionary principles. We may be the highest of beasts, but beasts we are still. If there is no God, then there is no heaven or hell or life after death. No matter what noble words the atheist uses to attempt to promote the dignity of his fellow man, he must return to the reality that his philosophy forces upon him: that man is but beast and to beast he will return. Period.

If that is the case, then the atheist really has no defense against all the forces of death. If human beings are no more than beasts, then the ethics of evolution apply: The weak die; the strong survive. If there is no God and human beings are beasts, then there can only be sentimental and squeamish resistances to human cruelty. If the law of the jungle prevails, then there can be no objection to tyranny, torture, imprisonment and genocide. If there is no God and human beings are beasts, then abortion and euthanasia are not more problematic than swatting a mosquito or putting a pet to sleep.

The second enemy of the Catholic belief in the dignity of each human person is materialism. By “materialism” I don’t simply mean “consumerism” or the need to shop until you drop. Instead, I mean the assumption that this world is all there is. The materialist is not consciously an atheist. Instead, he has drifted into a kind of atheism by default. Because he believes that this physical world is all that matters, he is indifferent to any greater meaning or purpose to life. When it comes to abortion, the materialist doesn’t much care one way or the other because he hasn’t really thought it through. This lazy philosophy is the default setting for the vast majority of Americans.

The third objection to the Catholic doctrine that each human being is an image of God is the doctrine of total depravity, held by some Protestants. They who hold this teaching believe that our first parents were created in God’s image but that original sin does not only wound that image, but destroys it. According to them, we are not totally and utterly evil, but the good that we do is poisoned with evil. The result of the doctrine of total depravity is to downplay the innate goodness of the human person and, therefore, the innate worth of the human person.

This does not mean that they are pro-abortion. Many good Protestants support the pro-life cause with great commitment. However, their underlying theology lends itself to a weakening of the pro-life argument. For them, humanity is not quite as wonderful as Catholics would like to maintain. That doesn’t mean they want to kill unborn children, but it does mean that the pro-life argument is somewhat weakened in the wider society.

Why is it that Catholics are the most ardent supporters of the pro-life cause? Because Catholic theology has a stronger emphasis on the preciousness of each human life. Each person is created in God’s image; each one has a God-given beginning and an eternal destiny. To destroy any human life, therefore, is to destroy an image of God.

This is also why the Catholic pro-life cause needs to be not just anti-abortion, but fully pro-life. We need to continue our efforts to promote adoption as the positive option. We need to continue our efforts to assist women in crisis pregnancies, to support men and women who have been wounded by abortion, and to do all we can to joyfully uphold marriage, children and family life and promote abstinence education — for every time we show ourselves to be pro-life, we show ourselves to be pro-God.

Father Dwight Longenecker is the parish priest of Our Lady of the Rosary Parish in Greenville, South Carolina. Visit his parish site to connect to his blog, books and articles.